Contactless or wireless communication is carried out between a reader and an object, for example, a transponder of the tag type, a contactless smartcard or else a mobile telephone emulated in a card mode. These examples are not to be limiting. The reader may also, for example, be a mobile telephone emulated in a reader mode.
Near-field communications, better known by those skilled in the art under the acronym NFC, is a technology for wireless connectivity which allows communications over a short distance, for example, 10 cm. This may be between electronic devices, such as, for example, contactless smartcards or mobile telephones emulated in a card mode, and readers. NFC technology is particularly suited to connecting any type of user device and enables fast and easy communications.
A contactless object is an object capable of exchanging information via an antenna with another contactless object, for example, a reader. The information may be exchanged according to a contactless communications protocol.
An NFC object, which is a contactless object, is an object compatible with NFC technology. NFC technology is an open technology platform standardized in the standards ISO/IEC 18092 and ISO/IEC 21481 but incorporates numerous already existing standards such as, for example, the type A and type B protocols defined in the standard ISO-14443 which can be communications protocols that may be used in NFC technology.
Aside from its conventional function of a telephone, a cellular mobile telephone may be used (if it is equipped with specific means or circuitry) for exchanging information with another contactless device, for example, a contactless reader, using a contactless communications protocol used in NFC technology.
This allows information to be exchanged between the contactless reader and secure elements situated in the mobile telephone. Numerous applications are thus possible, such as mobile ticketing in public transportation (the mobile telephone functions as a travel ticket) or mobile payments (the mobile telephone functions as a payment card).
When information is transmitted between a reader and an object emulated in a tag or card mode, the reader generates a magnetic field by its antenna which is generally, in the standards conventionally used, operates at a frequency of 13.56 MHz.
On the other side, the antenna of the object emulating the tag modulates the field generated by the reader. This modulation is carried out by modifying the load connected to the terminals of the antenna of the object.
By modifying the load across the terminals of the antenna of the object, the output impedance of the antenna of the reader changes due to the magnetic coupling between the two antennas. This results in a change in the amplitudes and/or the phases of the voltages and currents present on and in the antennas of the reader and of the object. So, in this way, the information to be transmitted from the object to the reader is transmitted via load modulation to the antenna of the reader.
Furthermore, the contactless charging technology allows the contactless transfer of energy from a source of energy (for example, a charger) to a load, for example, a wireless communications device such as a cellular mobile telephone, across the air space separating the charger and the load.
Among the various standards for contactless charging, the A4WP (Alliance for Wireless Power) standard is among one of the standards chosen by the main manufacturers of smart cellular mobile telephones (or smartphones).
Numerous publications exist on the specifications of the A4WP standard to which those skilled in the art can refer to at their convenience. The article by Ryan Tseng et al. may notably be cited, which is titled “Introduction to the Alliance for Wireless Power Loosely-Coupled Wireless Power Transfer System Specification Version 1.0,” IEEE Wireless Power Transfer Conference 2013, Technologies, Systems and Applications, May 15-16, 2013, Perugia, Italy.
In summary, contactless energy is transferred from a Power Transmitter Unit (PTU) to a Power Receiving Unit (PRU) controlled by a management protocol for the charging process. The contactless energy is generated at a frequency equal to 678 MHz.